Surgical anchors are used instead of surgical suturing, which is often both time consuming and inconvenient, in order to join two tissue locations. A surgeon can often use a stapling apparatus to implant an anchor into a body tissue and thus accomplish in a few seconds, what would take a much longer time to suture. A surgical anchor is used, for example in inguinal hernia surgery to fasten polypropylene mesh to the abdominal wall in order to reinforce the abdominal wall.
Surgical fasteners are known in the form of a staple in which a pair of prongs extends from a crown. In some applications, the body tissue is accessible from two opposite direction so that a deployment device may be used having an anvil that is used to bend the prongs towards each other after the prongs have penetrated through the tissue. In applications where access to the tissue is from one direction only, deployment device is used that delivers a force to the crown that deforms the crown and thus causes the prongs to project towards and grasp the tissue.
Applicant's co-pending application PCT/IL2006/000783 filed on Jul. 6, 2006, the contents of which are included herein in their entirety by reference, discloses surgical fasteners having two or more prongs, each of which is connected to a crown by hinge. In an undeployed configuration of the fastener, the tips of the prongs are inserted into slots in a base plate. The crown is thus separated from the baseplate in the undeployed configuration of the fastener by the length of the prongs. This configuration is stabilized by an engagement between the prongs and the baseplate, for example, by friction between the prongs and slot edges or by filling the slots with adhesive, glue or by a plug of softer material such as a biodegradable material. Deployment of such a fastener involves positioning the fastener at the site of a tissue surface where it is to be deployed and urging the crown towards the baseplate. As the prongs pass through the slots, they enter the tissue while the force applied to the prongs by the slot edges causes them to rotate at the hinges and splay radially outward from the crown so as to become embedded in the tissue. Only the prongs penetrate into the tissue, while the crown and baseplate become attach to the tissue surface without penetrating into it. The fastener may be used to attach a graft or a mesh to a body tissue.
As further disclosed in PCT/IL2006/000783, the above described fastener may become locked in its deployed configuration. Locking of the fastener in its deployed configuration allows the fastener to better withstand forces acting on it within the tissue and thus prevents inadvertent release of the fastener from the body tissue. The locking is accomplished by means of an engagement between components of the fastener that increases the force necessary to bend the extended prongs of the deployed fastener closer to the longitudinal axis of the fastener compared to situation in which locking means are not provided. The locking may be due to an engagement between the prongs and the crown, the prongs and the baseplate, or the crown and the baseplate. For example, the locking may result from increased friction between the prongs and slots due to a region along the length of the prongs of increased width or thickness that enters the slot during deployment, so that the prong becomes jammed in the slot. The prongs may be locked in the deployed configuration by engagement of a tongue extending from each slot of the second element into an opening in the prong. Alternatively, a tongue in the prong may engage an opening in the second element.